Total retail sales in the U.S. topped $4.53 trillion in 2013, and e-commerce accounted for a significant portion of that growth, up 16.9 percent in 2013 — or nearly $40 billion — according to new figures from eMarketer.

According to the company, this is eMarketer's first-ever benchmark of total retail and retail store sales, which are based on a multimodel analysis of 169 data points that eMarketer gathered from 47 research firms and government institutions. The forecast separates retail e-commerce sales — including all purchases made on desktop and laptop computers, tablets and mobile phones — and non e-commerce sales, which mostly comprise brick-and-mortar retail purchases.

Retail growth is a reflection of what's happening in the broader economy, which is gaining momentum. The Dow Jones Industrial Average reached a new high early in 2014, and consumer confidence, as measured by The Conference Board's Consumer Confidence Index, rose in February after three months of decline. Total retail sales are leading economic growth, increasing 4.2 percent in 2013, according to eMarketer's forecast, which projects total retail sales to accelerate further in 2014, increasing 4.4 percent to reach $4.732 trillion this year.

In 2013, retail represented 27.0 percent of nominal U.S. gross domestic product (GDP), up from 26.8 percent in 2012, comparing eMarketer figures against GDP figures from the U.S. Department of Commerce. That share has been increasing consistently since a drop-off in 2009, when consumer confidence was at a low after the recession.

While brick-and-mortar sales still command a vast majority of the retail market — nearly $4.27 trillion in 2013 — e-commerce sales are increasing much faster, contributing significantly to retail's overall growth throughout the forecast period. eMarketer estimates that U.S. retail e-commerce sales will increase 15.5 percent in 2014 to reach $304.1 billion, up from $263.3 billion in 2013. E-commerce growth will represent more than 20 percent of this year's increase in total retail sales.

E-commerce still represents a small portion of overall retail sales — a mere 5.8 percent last year. However, e-commerce will continue to increase in the double digits year over year to bring its share of overall retail to almost 9 percent by the end of the forecast period.

Mobile retail sales are on a rapid rise as well, steadily gaining share of overall e-commerce. In 2013, retail m-commerce — which includes products and services ordered on mobile devices, including tablets — increased 70.0 percent to reach $42.13 billion. eMarketer estimates that in 2014, that figure will increase another 37.2 percent to total $57.79 billion, or about one-fifth of all retail e-commerce sales and 1.2 percent of total retail sales. In 2014, tablet sales will account for nearly two-thirds of m-commerce sales, eMarketer predicts, increasing to nearly 75 percent of all mobile retail sales by the end of the forecast period.